Dangerous goods include liquid or solid substances, and articles containing them, that have been classified according to internationally-agreed criteria, and found to be potentially dangerous (hazardous) during transportation and/or storage. Most countries base their legislative requirements for storage and transportation of dangerous goods on the “Recommendations on the transport of dangerous goods” issued by the United Nations and the United Nations' prescribed testing codes for establishing the acceptability of various packaging and transportation methods.
Dangerous goods are assigned to different Classes depending on their predominant hazard, and on the basis of the specific chemical characteristics posing the risk. Such Classes include the following: class 1, explosives; class 2, gases; class 3, flammable liquids; class 4, flammable solids; class 5, oxidizing materials and organic peroxides; class 6, toxic and infectious substances; class 7, radioactive materials; class 8, corrosives substances; and class 9, miscellaneous (including asbestos, dry ice, engines, etc.). Except for very small packages, all packages and containers, shipping containers, unit loads, tankers, etc. which hold dangerous goods for transport must carry the correct Class Label. This label shows the nature of the hazard by the colour and symbol, and the Class of the goods by numeral. The Recommendations specify how storage areas are to be designed, constructed and located to minimize risks. The Recommendations are designed to assist the authorities and other emergency services, and to ensure that they have enough information to deal with incidents.
According to the United Nations classification system, explosives are also assigned compatibility group letters to facilitate their segregation during transportation. The letters used range from A-S, except for the letters I, M, O, P, Q and R. Also, they are sub-classified using the following sub-classes: 1.1 for explosives with a mass explosion hazard; 1.2 for explosives with a severe projection hazard; 1.3 is for explosives with a fire, blast or projection hazard but not a mass explosion hazard; 1.4 stands for minor fire or projection hazard (includes ammunition and most consumer fireworks); 1.5 is for an insensitive substance with a mass explosion hazard; and 1.6 for extremely insensitive articles. In the explosives industry, it is preferred to attempt to package some explosives such as detonators in such a way as to reduce their hazard classification from 1.1 to 1.4, so that the explosive substances as packed represent only a minor fire or projection hazard. This provides far greater levels of safety and allows for much cheaper transportation costs. In the case of detonator packaging, this certification relies on the fact that they are packed and designed so as to confine most of the effects of any accidental explosion or ignition within the package itself, and if there are multiple devices, one detonator exploding will not lead to mass detonation of the others in the package.
In order for detonators to be certified as 1.4, they must pass the UN Test Series 6 external fire test (Bonfire test), which may include Tests 6(a), 6(b), 6(c), and 6(d). The packaging can have a significant influence on the explosive effects of substances and articles. The type of packaging can change the response of packed explosives or explosive articles in Test Series 6. One and the same explosive substance or article can therefore be assigned to different hazard groups, or even be rejected from Class 1 for transport depending upon the packaging used. The Bonfire test is performed on packages of explosive substances or explosive articles, or unpackaged explosive articles, to determine whether there is a risk of mass explosion or a potential hazard from dangerous projectiles, radiant heat and/or violent burning or any other dangerous effects. Typically, a stack of test substances or articles is placed on a non-combustible surface (steel grate) above a lattice of dried wood soaked with diesel fuel or equivalent source. A wire basket or clamps may be used to hold the articles in place. Sufficient fuel is used to provide a 30-minute fire. Three aluminum witness plates, each having a surface area of 4 m2 (2 m×2 m), are placed away from the edge of the packages at a distance of four meters. The fire is ignited and the material is observed for:
a) Evidence of detonation, deflagration or explosion of the total contents;
b) Potentially hazardous fragmentation; and
c) Thermal effects (i.e. size of the fireball, etc.).
The results are used to determine whether a reaction from an explosive article in its package, which was accidentally fired or initiated, would propagate to other articles or parts of the process. The package product is assigned a 1.4 certification if it meets the following requirements:
1) no indentations of the witness plates are observed; and
2) no projection, thermal effect or blast effect is observed.
With respect to the transportation and storage of detonators, the relevant criteria are generally accepted to be the UN 1.4 Code of testing. This certification relies upon the fact that when detonators are packed together for storage and/or transportation, inadvertent initiation of one detonator will not lead to mass detonation of other detonators present. This is especially important for air transportation since it is the most restricted mode of shipping. For such transportation, the 1.4S classification is required, the “S” being indicative that any hazardous effects arising from accidental functioning of the detonators in a package is confined within the package (unless the package has been degraded by fire, in which case all blast or projection effects are limited to the extent that they do not significantly hinder or prohibit fire fighting or other emergency response efforts in the immediate vicinity of the package).
Previously, packaging methods for the storage and transport of shelled detonators have included the use of protectors on the detonators or specially designed transportation boxes. For example, International Patent Publication WO95/19539 published Jul. 20, 1995, discloses a protector for use in the transportation and storage of detonators, comprising a detonator holder which is open at one end for insertion of a detonator, and closed at the other end, and which radially encloses the base charge of said detonator, at least one detonator retaining means integral with the detonator holder, and a first wall which is radially spaced around the holder and wherein the holder and wall define a space. In use, the detonator retaining means holds the detonator within the holder such that a free volume is provided around the base charge of the detonator.
Another example is U.S. Pat. No. 5,133,258 issued Jul. 28, 1992, which discloses a safe transportation holder and package for explosive devices such as blasting caps. Each cap is contained in an internal cavity in a holder, and surrounded by radially-spaced, elastomeric walls. The holders are arrayed in a container, and absorb the energy released by accidental detonation of one cap to prevent sympathetic detonation of others in the packages.
U.S. Pat. No. 6,454,085 issued Sep. 24, 2002 discloses a system and method for packaging shaped charges for transportation. Each shaped charge includes a housing and a liner having a high explosive disposed therebetween. A jet spoiler is positioned proximate the liner of each of the shaped charges to prevent the formation of a jet in the event of an inadvertent initiation of a shaped charge. The shaped charges are then oriented in first and second layers such that the jet spoilers positioned proximate the liners of the shaped charges in the first and second layers oppose one another. A shielding panel is disposed between the shaped charges of the first and second layers. The shaped charges including the jet spoilers and the shielding panel are placed within an expandable bag which is in turn enclosed within a transportation container. The jet spoilers may be constructed of a suitably dense material such as wood, plastic, foam, rubber, plaster, cement and the like. Ideally the material would be one that is environmentally friendly for easy disposal, lightweight to facilitate shipping and handling and economical. For example, biodegradable cardboard, balsa wood or compressed sawdust are suitable materials. The expandable bag is preferably made from a ballistic cloth, and the container may preferably be a corrugated cardboard box or a wood box.
U.S. Pat. No. 6,629,597, issued Oct. 7, 2003, discloses a system and method for packaging shaped charges for transportation. Each shaped charge includes a housing and a liner having a high explosive disposed therebetween. A jet spoiler is positioned proximate the liner of each of the shaped charges to prevent the formation of a jet of shrapnel in the event of an inadvertent initiation of a shaped charge. The jet spoilers may be comprised of a metal or non-metal material. Wood, plastic, rubber, plaster, cement, cardboard, balsa wood, or compressed sawdust are disclosed as particularly suitable attenuator materials for the jet spoilers. The shaped charges are then oriented in first and second layers such that the jet spoilers positioned proximate the liners of the shaped charges in the first and second layers are opposite one another. A shielding panel is disposed between the shaped charges of the first and second layers. The shaped charges, including the jet spoilers and the shielding panel, are placed within an expandable bag which is in turn enclosed within a transportation container.
As a further example, U.S. Pat. No. 4,286,708 discloses a package wherein the sympathetic or chain reaction detonation of stacked munitions is prevented by confining any random explosion essentially to a single explosive unit or container. Frangible inhibitor plates are located between adjacent munitions, such as artillery shells, so as to isolate the adjacent explosive units from a residual shock wave or case fragment that would otherwise trigger sympathetic detonation. The inhibitor plates may be constructed as part of a container in which an artillery shell may be stored, or the plates may be separately inserted between any adjacent warhead in any conventional storage pallet or transporting configuration. The plates are designed to absorb only that amount of explosive energy required to prevent sympathetic detonation, without requiring that the explosive forces be redirected away from adjacent shells, thus reducing the problem of redirected blast.
Other packaging methods involve wrapping a detonator in its down-hole wire, and caging a box of detonators within its cardboard box. For example, Canadian Patent application 2,118,528 discloses a non electric detonator assembly for its safe transport in bulk wherein a detonator is located substantially along the axis of a coil of initiation tubing, the initiation tubing being wound such that it may be unwound by drawing from the centre of the coil.
Another method used for packaging explosive devices such as detonators is one inspired by the military industry. It involves the use of a cardboard tube having a clay plug or equivalent thereof at one end. Such equivalents to a clay plug may include, but are not limited to, a plug comprising wood, compressed sawdust, cement, granulated sand, plaster, dry wall materials, and other materials. The device is enclosed in the tube, with its explosive end at or near the clay plug end. The plug acts, at least in certain circumstances, as a jet spoiler to absorb shrapnel from an explosion, and the tube functions as a flame retardant. The tube is preferably made of cardboard because this material is not too dense, inexpensive and environmentally benign. Examples of this packaging method can be found in United States Patent Applications published as 2005/0150781 and 2006/0108237 on Jul. 14, 2005 and May 25, 2006 respectively. US 2005/0150781 discloses a detonator protector including a housing fitted with an end cap at one end and a plug at the other end. US 2006/0108237 discloses a tubing assembly having opposed ends and a thick wall of relatively low-density fibrous material, and having an impact absorbing element positioned at each end of the tube.
Although numerous methods for the storage and transport of dangerous goods have been developed, there remains a continuing need to develop improved methods to increase security and safety of dangerous goods, and in particular explosive devices such as detonators. Moreover, there remains a continuing need to develop packaging methods for storage and transportation of detonators, with improved protection against inadvertent mass initiation of other detonators within a package.